Topic: My DIY Jecklin

[thunderbolt]

Here's my Jecklin.

Built it to his later specs, 35 cm disc (3/8" oak plywood) and 36 cm between capsules.  A friend of mine did the woodwork, cutting the shape like a ping-pong paddle, with a tongue (the "handle") to slide into the groove of a tapered piece of 4x4.  I attached felt using spray adhesive, and then used 1/2" high density foam, which I velcroed to the disc (so that different width foam or material can be used).  The mic fittings are a hodge-podge, but allow for infinite adjustability, including using Jecklin's original spacing between mics (16.5 cm).

I tried to stay as faithful as I could to technique and measurements.  Maiden voyage soon.

Corbin

[H₂O]

that's pretty!

[Fried Chicken Boy]

Very cool!  I'd like to hear the results after its maiden outing.

[Gutbucket]

Nice.  I prefer the additional timing info of the later Jecklin specs, even though it is less slim overall.

If you are one to obsess over details, it may be advantageous to have the felt on the outside of the dense foam layer.  I suspect the foam may reflect high frequencies that the felt would absorb.  The foam will probably absorb slightly lower frequencies (lower treble, upper mids) better, but would do that just as well beneath the felt layer.   The basic strategy is to put the material targeting the highest frequencies on the outside.  When I was playing around with this a few years ago I layered a few different materials and held the test disk angled close to the front of a speaker so the disk reflected the driver's output to my ear, with the direct sound to my ears blocked, and the disk acting as a sonic mirror.  The difference in materials was easily audible while rotating the disk so that the sound reflected directly towards my ear or not. 

But the best advice is probably not to worry about it and just enjoy using it.  As a practical matter it's far more important where you put the thing.

[thunderbolt]

Interesting point about felt over the foam.  It seemed as though more than a few people who covered theirs in sheepskin or fake fur felt it resulted in more restricted high frequencies, so I figured I'd go minimal at first.  Making a felt sleeve might be a next step.  Thanks for your feedback.

[Gutbucket]

Most Jecklin disk recordings need a shelving treble boost regardless of covering, IME.  Sure you may need a bit more boost if the highs aren't boosted by reflections off the surface (I suspect the boost is from a comb fitering effect of the sum after the bounce more than the reflected energy alone), but using the reflectivity of the disk itself as a tone control is counter to the whole idea of the thing since it's designed to block the sound, instead of reflect it. 

Embrace the EQ either way you go.

[Fried Chicken Boy]

... it may be advantageous to have the felt on the outside of the dense foam layer.  I suspect the foam may reflect high frequencies that the felt would absorb.  The foam will probably absorb slightly lower frequencies (lower treble, upper mids) better, but would do that just as well beneath the felt layer. [snip]

So, ideally, is it best to have the surfaces of a Jecklin disk acoustically "dead" or as close to it as you can?  Somewhat as recording binaurally on both sides of a human head?  Asking as I've never used one but I like the theory behind it.

[Gutbucket]

That's the theory.  How important that is in the real world is open to debate.  FWIW, Mr Jorg Jecklin doen't seem to worry about it too much as there appears to be just a single realtively thing layer of foam on his in the photos I've seen, but what the actual absorbtion charateristics of that foam are, I don't know.

[thunderbolt]

Here it is in its winter fleece....